Experiments on the spread of colds: II. Studies in volunteers with coxsackievirus A21

Abstract

The amount of virus in nasal and other secretions after infection with coxsackievirus A 21 has been measured daily in ten volunteers. Most virus was found in nasal secretion, less in throat secretion and small amounts were found intermittently in the saliva and faeces.Virus administered as small drops or on a swab was more infectious for man if put on to the nasal mucosa than on to the throat or outside the nose. It was also infectious by the conjunctival route.Virus was sprayed in droplets of about the same size range as those found in a natural sneeze. Virus survived better in larger (> 4 μ) than in smaller droplets. About one tissue culture infectious dose of virus in such droplets also infected volunteers.The symptoms produced by these experimental infections have been analysed. The disease produced was largely independent of the dosage and route of infection. Those with pre-existing antibody resisted infection better than those with no antibody. Antibody rises were detected in about two-thirds of infected volunteers.Volunteers with colds shed virus in large drops on sneezing, or into the handkerchief on blowing the nose, but virus was recovered from the air only after simulated sneezes by volunteers with high concentrations of virus in their nasal secretions. Virus died off rapidly on fabric at room temperature and humidity, and was only resuspended as airborne droplets when large doses such as 0·02 ml. of virus of high titre (107·5 TCD 50/ml.) were used.Infection was transmitted from an infected volunteer to an uninfected partner living in the same flat in three out of twenty tests. Infection was not transmitted in experiments when volunteers mixed for a few hours with subjects with colds, or inhaled air into which a subject with a cold had just sneezed.